Her Majesty The Queen dedicated a public memorial at Bletchley Park, Milton Keynes, Buckinghamshire on Friday 15 July, to commemorate all those that provided vital service at Bletchley Park and its ‘Outstations’ during World War II.

This was The Queen and Duke of Edinburgh’s first visit to the home of the wartime code breakers. They were accompanied throughout the visit by Sir Francis Richards, Chairman of the Bletchley Park Board of Trustees and Simon Greenish, Director of the Bletchley Park Trust.

The Royal Party was provided with a short tour of the museum and shown some of the restoration projects which have taken place at Bletchley Park to rebuild the machines which assisted with the wartime decryption of enemy codes. These included the Turing Bombe, brainchild of mathematical genius Alan Turing, and Colossus, the world’s first electronic computer. The Queen was also shown an Enigma machine and given a demonstration of how it worked.

At the dedication ceremony, The Queen was introduced to some of the veterans that either served at Bletchley Park or the ‘Outstations’, that intercepted the materiel that Bletchley Park processed. These included Sir Arthur Bonsall, veteran of the Bletchley Park air section, who went on to be a Director of GCHQ. She was also introduced to some of the relatives of deceased veterans, who had been invited to celebrate the event, including Sir John Dermot Turing, nephew of Alan Turing.

Before she unveiled the memorial, The Queen spoke of her deep sense of admiration and gratitude for the men and women who served at Bletchley and the debt the nation owes to them for their achievements. She also emphasised the importance of the intelligence allies with whom the UK worked, and the inspiration Bletchley provides to the intelligence services today, as they continue their vital work of protecting the people of this country.

Following the ceremony, The Queen was shown the Roll of Honour which lists the names of all of those who served at Bletchley Park and its ‘Outstations’ during the War. This has been compiled over a number of years and includes nearly 11,000 names.

Mrs Sheila Lawn, a veteran of Bletchley Park, said after the ceremony: “It was a very great honour, a great pleasure and the culmination of a great deal of effort to have such a splendid occasion at Bletchley Park with Her Majesty The Queen and His Royal Highness The Duke of Edinburgh present”.

2. The memorial was designed and sculpted by artist Charles Gurrey. Commissioned by The Bletchley Park Trust and GCHQ (successors to GC&CS), it fulfils a commitment by the previous Foreign Secretary, David Miliband, to provide a lasting tribute to the Bletchley Park veterans.

The memorial consists of two, eight foot high slabs of Caithness stone interlinked at the top. This signifies the mutual reliance of those that worked at Bletchley Park and those that intercepted enemy transmissions at the ‘Outstations’. One block displays the wording ‘We also served’ and the other a sculpted list of some of the 300 plus outstations that existed across the world. There is also a Morse code message engraved on the back of the memorial, which says ‘My Most Secret Source’. This was one of Churchill’s famous expressions, describing the valuable ‘Ultra’ intelligence, obtained from the decryption of Enigma intercepts.

3. Bletchley Park is the wartime home of the Government Code and Cypher School (GC&CS). At the height of World War II, the code breakers of Bletchley Park decoded enemy messages, included ciphers generated by the famous Enigma machine, on an industrial scale, giving the Allies a huge advantage. Many historians believe that the Bletchley Park code breaking effort shortened the war by at least two years, saving an incalculable number of lives.

4. The Turing Bombe was an electromechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted signals during World War II. The US Navy and US Army later produced machines to the same functional specification, but engineered differently.

The initial design of the bombe was produced in 1939 at the UK Government Code and Cypher School at Bletchley Park by Alan Turing, with an important refinement devised in 1940 by Gordon Welchman. The engineering design and construction was the work of Harold Keen of the British Tabulating Machine Company. It was a substantial development from a device that had been designed in 1938 by Polish Cipher Bureau cryptologist Marian Rejewski, and known as the "cryptologic bomb" (Polish: "bombakryptologiczna").

The function of the bombe was to discover some of the daily settings of the Enigma machines on the various German military networks: specifically, the set of rotors in use and their positions in the machine; the rotor core start positions for the message—the message key—and one of the wirings of the plugboard (wikipedia).

5. Colossus - The Colossus machines were electronic computing devices used by British codebreakers to help read encrypted German messages during World War II. They used vacuum tubes (thermionic valves) to perform the calculations.

Colossus was designed by engineer Tommy Flowers with input from Harry Fensom, AlleCoombs, Sidney Broadhurst and William Chandler at the Post Office Research Station, Dollis Hill to solve a problem posed by mathematician Max Newman at Bletchley Park. The prototype, Colossus Mark 1, was shown to be working in December 1943 and was operational at Bletchley Park by February 1944. An improved Colossus Mark 2 first worked on 1 June 1944, just in time for the Normandy Landings. Ten Colossi were in use by the end of the war.

The Colossus computers were used to help decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machine—British codebreakers referred to encrypted German teleprinter traffic as "Fish" and called the SZ40/42 machine and its traffic "TUNNY". Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.

The Colossus was used to find possible key combinations for the Lorenz machines – rather than decrypting an intercepted message in its entirety.

In spite of the destruction of the Colossus hardware and blueprints as part of the effort to maintain a project secrecy that was kept up into the 1970s—a secrecy that deprived some of the Colossus creators of credit for their pioneering advancements in electronic digital computing during their lifetimes—a functional replica of a Colossus computer was completed in 2007 (wikipedia).

6. Enigma – Enigma is a family of related electro-mechanical rotor machines used for the encryption and decryption of secret messages. The first Enigma was invented by German engineer Arthur Scherbius at the end of World War I. This model and its variants were used commercially from the early 1920s, and adopted by military and government services of several countries — most notably by Nazi Germany before and during World War II. Several different Enigma models were produced, but the German military models are the ones most commonly discussed.

In December 1932, the Polish Cipher Bureau first broke Germany's Enigma ciphers. Five weeks before the outbreak of World War II, on 25 July 1939, in Warsaw, the Polish Cipher Bureau gave Enigma-decryption techniques and equipment to French and British military intelligence.

Thanks to this, during the war, Allied codebreakers were able to decrypt a vast number of messages that had been enciphered using the Enigma. The intelligence gleaned from this source, codenamed "Ultra" by the British, was a substantial aid to the Allied war effort.

The exact influence of Ultra on the course of the war is debated; an oft-repeated assessment is that decryption of German ciphers hastened the end of the European war by two years. Winston Churchill told Britain's King George VI after World War II: "It was thanks to Ultra that we won the war."

Though the Enigma cipher had some cryptographic weaknesses, in practice it was only in combination with other factors (procedural flaws, operator mistakes, occasional captured hardware and key tables) that those weaknesses allowed Allied cryptographers to be so successful (wikipedia)